1. Field of the Invention
The present invention relates to a resistor for an electron gun assembly that is mounted in a cathode-ray tube apparatus, and more particularly to a resistor for an electron gun assembly, the resistor being configured to apply a voltage, which is divided with a predetermined resistance division ratio, to a grid electrode provided in the electron gun assembly, an electron gun assembly with the resistor, and a cathode-ray tube with the resistor.
2. Description of the Related Art
In general, a cathode-ray tube that is used in a color TV receiver includes an electron gun assembly that emits electron beams toward a panel. The electron gun assembly includes a plurality of grid electrodes. Specifically, the electron gun assembly includes various grid electrodes that are supplied with relatively high voltages, as well as an anode that is supplied with an anode voltage.
In this cathode-ray tube with the above-described structure, if a high voltage is applied to each of the grid electrodes from a stem section of the cathode-ray tube, a problem relating to withstand voltage arises. To solve the problem, a resistor for dividing a voltage, which functions as a resistor for an electron gun assembly (hereinafter referred to simply as “resistor”), is incorporated along with the electron gun assembly in the cathode-ray tube. The resistor divides a voltage at a predetermined resistance division ratio, thereby applying a desired high voltage to each of the grid electrodes.
The resistor includes, on an insulating board, an electrode element formed of a low-resistance material, and a resistor element formed of a high-resistance material that is basically similar to the material of the electrode element. A part of the electrode element and the resistor element are coated with an insulating coating layer. A terminal portion that is formed of a metal terminal is electrically connected to the electrode element. The terminal portion is fixed by calking to a through-hole that is formed in the insulating substrate (see, e.g. Jpn. Pat. Appln. KOKAI Publication No. 6-68811).
As regards the above-described electron gun assembly including the resistor, if the arrangement of grid electrodes or the resistance division ratio is altered in order to improve focus characteristics, the position of the terminal of the resistor will also inevitably be altered. It is thus necessary to prepare an insulating substrate that has a different position of the through-hole in accordance with the type of the electron gun assembly, or to prepare a screen having a different pattern. This may lead to a decrease in manufacturing yield.
In addition, it is necessary to adjust the resistance value of the resistor element that is formed on the surface of the insulating substrate of the resistor, thereby making it possible to supply the grid electrode with a voltage that is divided with a predetermined resistance division ratio. There is a case, however, where a predetermined resistance division ratio cannot be obtained in the vicinity of the-output terminal for output to the grid electrode, due to constraints in space of the insulating substrate. Consequently, a desired performance of the electron gun assembly may not be achieved, and the reliability may deteriorate.